Method for pressing corrugated cardboard flat in places



June 9,- 1931. CLEMENS 1,309,472

METHOD FOR PRESSING CORRUGATED CARDBOARD FLAT IN PLACES Filed April 18, 1928 Jbvaviar:

Patented June 9, 1931 UNITED STATES PATENT OFFICE L'UDWIG CLEMENS, OF BERLIN, GERMANY, ASSIGNOR TO THE'FIRM WEZEL & NAUMANN AKTIENGESELLSOHAFT,

OLE LEIPZIG, GERMANY METHOD FOR PRESSING CORRUGATED CARDBOARD FLAT IN PLACES Application filed April 18, 1928, Serial No. 270,998, and-in Germany May 10, 1927.

When applying advertising matter in the form of pictures and letterpress to corrugated cardboard, various methods have hitherto been adopted. The places on the cardboard which are to be provided with the pictures and letterpress have been punched out and paper stuck behind them, which acted as a base for the pictures and letterpress to be stuck on. Another method has been to m stick on the punched-out place a sheet with the required picture with a gummed strip.

According to the present invention the place intended to be used for the advertising matter is prepared by pressing the corrugations flat in the area in question, so that the sheet with the advertising matter can be stuck directly on the corrugated cardboard base. This has the disadvantage, that on the surface of the corrugated cardboard a fluting of the thickness of the paper remains which is caused by the corrugations laid over sideways by the die during the pressing operation, which have a disturbing eflect more particularly when the sheet of advertising matter contains representations of figures.

This drawback may be overcome, by the corrugated cardboard being pressed over a yielding foundation, whereby the completely flat upper surface is produced, as the folds causing the fluting cangive way downwards,

thus appearing only on the reverse side.

In the accompanying drawings Fig. 1 shows the first stage in the pressing operation and Fig. 2 the final stage of the pressing operation according to the present invention.

a is the lower sheet of paper of the corrugated cardboard which is substantially fiat before the pressing operation and b the upper corrugatedsheet of paper of the corrugated cardboard. At 0 is indicated how the corrugations of the upper sheet 7) in the first place are laid over flat on the pressing die, being applied and show a distinct fluting on thev e impressed with the picture or the like forming theadvertisement is stuck.-

The yielding base used in pressing consists of any suitable material for instance fine felt, which, while it is capable of withstanding the high pressure, used in pressing is so yielding that during the pressing operation it yields to the downwardly forced fiuting and is pressed right into it. The yielding base may also consist of superimposed sheets of blotting paper or of Klingerit which is a well known packing material used in stufiing boxes and the like. The base is either so surface during each operation disappears again as soon as the pressure is released or the'material, of which the base is made is so plastic that during a following operation the ribs left in the base from the previous operation disappear again and fresh depressions are formed in the base by the downwardly elastic that the fluting formed in its working 

